4.13 Sound Intensity

Sound intensity is measured in

• N

• W

• N/m²

• W/m²

Sound becomes audible to the human ear at an intensity of

• I₀ = 10³ W/m²

• I₀ = 10¹² W/m²

• I₀ = 10^-3 W/m²

• I₀ = 10^-12 W/m²

The decibel (dB) measures

• sound intensity

• sound intensity level

• how large a speaker is

• the electric potential difference across a speaker

If we can already measure intensity in W/m², why do we need decibels?

• dB is used specifically for speakers

• dB takes distance into account

• dB compares how much more intense a sound is compared to the quietest sound that we can hear as a difference

• dB compares how much more intense a sound is compared to the quietest sound that we can hear as a ratio

A 30 dB sound is ___________ than the quietest sound we can hear.

• 3 times greater

• 30 times greater

• 10 times greater

• 1000 times greater

Select all examples of sound intensity dissipating across larger distances.

• You can't hear your friend shouting at you from across the parking lot.

• You can't hear your friend speaking to you in the car because she's whispering too quietly.

• From your classroom, you can hear the quiet sound of applause coming from the school assembly in the school theatre.

• From your classroom, you can hear the quiet sound of classical music being played from your classroom speakers while you work.